Process for electrodepositing chromium and the like



March 22, 1932. w A. TYRRELL 1,850,426

PROCESS FOR ELECTRODEPOSITING CHROMIUMAND THE LIKE 5 Sheets-Sheet 1 INVENTOR Wmatgi Filedv July 15 1926 IHHHII-HH'H MarchZZ, 1932. w. A. TYRRELL 1,850,426

I PROCESS FOR ELECTRQDEPQSITING CHROMIUM AND THE LIKE Filed July 15, 192 5 Sheets-Sheet 2 INVENTOR By it ney,

March 22, 1932 w. A. TYRRELL PROCESS FOR ELECTRODEPOSITING CHROMIUM AND THE LIKE 5 Sheets-Sheet 3 Filed July 15, 1926 INVENTOR Q By Aliorn y Y W. A TYRRELL March 22, 1932.

PROCESS FOR ELECTRODEPOSITING CHROMIUM AND THE LIKE Filed July 15, 1925 March 22, 1932. TYRRELL 1,850,426

PROCESS FOR ELECTRODEPOSITING CHROMIUM AND THE LIKE Filed July 15, 1926 5 Sheets-Shef 5 Fzyl. 5

, a I V ,35

INVENTOR l mw fijra .z graf Patented 22, 1932 UNITED STATES PATENT OFFICE j AYBES OI IEBBICK, YORK, ASSIGNOB TO CHEMICAL TREAT- KENT comm, INC, OF NEW YORK, N. Y, A CORPORATION 01 NEW YORK PROCESS FOR ELECTBODEPOSI'IING CIBOHIUH AID THE LIKE Application filed July 15,

chromium or the like on the interiors of vessels, tubular articles, pipes and the like, and to apparatus therefor. It further relates to a process and apparatus for electrolytic clean- The invention provides a convenient, practical, and etfective process of electrodepositing chromium or the like on the interior of vessels, tubes, pipes, and the like, andparticularly upon the interiors of elongated articles; it also provides, an improved process and apparatus for effecting electrolytic cleanmg.

The accom anying drawings illustrate several modes "carrying the process into practice.

Figure 1 is a longitudinal sectional view through a plating tank, showing one mode of carrying out the process.

F1g. 2 is a cross section on the line 11-11,

Fig. 1.

Fig. 3 is a detail view, looking at one end of the apparatus in the direction of the arrows IIIIII, Fig. 1.

Fig. 4. is a view similar to Fig. 2, showing a longitudinal section of a chromium plating tank, and showing another mode of carrying the process into practice.

Figs. 5 and 6 are detail views, Fig. 5 being a section on the line V-V, Fig. 4, and Fig. 6 being an end view looking in the direction of the arrows VIVI, Fig. 4.

Fig. 7 is a longitudinal view'through the chromium plating tank, and illustrating a third mode of applying the process.

Figs. 8 and 9 are detail views, Fig. 8 bein a section on the line-VIII-VIII, Fig. 7, an Fig. 9 being an end view looking in the direction of the arrows IXIX, Fig. 7

Fig. 10 is a longitudinal sectional view through a chromium plating bath, and illustrates a mode of carrying the invention into practice somewhat similar to that illustrated in Fig. 1, the object being a tube closed at one end. Fig. 11 is a cross-sectional view on line XI-XI, Fig. 10.

Fig. 12 is also a longitudinal sectional view through a chromium plating bath and illus trates a mode of carrying the invention into 1926. Serial 1.. 122,513.

practice similar to that illustrated in Fig. 10. Fig. 13 is a longitudinal sectional view through a chromium plating bath andillustrates a mode of carrying the invention into practice somewhat similar to that illustrated in Fig. 7. Fig. 14 is a longitudinal sectional view through a chromium plating bath, and illustrates a fourth mode of carrying the invention into practice.

Fig. 15 is a cross-sectional view on the line XV XV, Fig. .14.

Fig. 16 is a detail view illustrating a shield bceltween the anode and portions of the oatho e.

According to the present invention, the

article to be plated, as for example a long pipe or tube such as shown in Figs. 1 to 9, inclusive, or a vessel, as shown in Fi 13 and-14, or a tube closed at one end, as s lawn in Figs. 10 and 12 has a suitable plating solution introduced into the inside thereof. The process of electrodeposition will be described .with particular reference to chromium plating, though the process may be used to advantage n plating such metals from baths where relatively large quantities of hydrogen .areevolved, and where current densities of considerable amount are reuired before plating is initiated or is ofective. v The solution is most conveniently introduced into the article by supporting the object horizontally or slightly inclined, immersed,'or partially immersed, in the solution in a long tank. The article itself may however in some cases be made to serve as a tank, as shown in Fig. 12.

- The plating solution is preferably a solutionof chrom1c acid containing sulphate radicals as a catalyst, as described in the Fink Patent No. 1,581,188, granted April 20, 1926, and the plating is carried on according to the conditions as to temperatures, current density, etc. described in said atent.

The anode is placed lengt wise of the article, on the inside thereof, and the article is made cathode by suitable connections.

en which is evolved is removed in a be efin the hydro suitab e manner. This removal may fected by inclinin the cathode artic e bath, as illustrate in Fi 1, in such manner that the hydrogen flows y gravity through the upper end ofthe article.. Where the ar- "ticle iso en at both ends, a circulation is indueed w ich assists in the removal of the hydro n. The removal of the hydrogen may a so be effected by placin a pipe inside of the article and drawing 0 the hydrogen from one or both ends. The hydrogen may be drawn off through the ipe, or the pipe may be used to introduce so ution into the article and force thehydrogen out at any desired rate., The article may be horizontal,

or inclined'to any desired extent.

Hydrogen may also be removed by so immersing the article in the bath or fi mg the article that a space .is left above the level of the bath, to which the hydrogen may es- 1 surface which are asyet unplated are prolater takes place thereon, the chromium plate 'leased in plating the entire inside of the tected from oxidation, so that when plating will adhere, and" an integral adherent plate roduced all around the inside of the article. his protection is afforded by covering the unplated. surfaces with the bath solution, as by wettingor by complete immersion, or by hydrogen.' Where the unplated surface is tobe rotected by the hydrogen, its escape is re erably retarded. I

' current of appropriate density for electrodepositin chromium along a strip may be effected y locating the anode closer to p the strip of surface to be lated than to the other portions of the sur ace, or by shielding the anode from the other portions of the surface, or otherwise. Moreover, it is preferable to shield the anode from the portions of the cathode on which plating is not being effected at the time, in order to conserve current, inasmuch as all that part of the c urrent flowing to the cathode below the necessary current density for electrodepositing chromium, is-ineifective and therefore lost.

On inside surfaces cleaning is frequently verydiflicult. A strong cleaning action, resulting inexcellent cleaning may be elfected by concentrating the current at portions of the surface and effecting a progressive clean- It ing, the apparatus being similar to that described for. plating, ancl an acid bath, pref erably concentrated sulphuric acid used in stead of the plating solution. The article ismade cathode. I

Referring to the'illustrated examples of the process and a paratus, and first to Fig. 1, numeral 10 designates atank containing suitable chromium platin solution (such'for exam' le as described in ghe Fink atent referre to above), and the cath e article, T

here shown as a long pi G, is immersed in the bath, and suspen ed in an inclined position by means ofsuitable hangers 15, 16, these hangers conveniently makin connection with a cathode bus bar 20,,whic thereby places said bus bar and cathode article in electrical connection. Sleeves or other suitable extensions 22, 23 are preferabl placed ing the position of the anode. 26 designates an anode bus-bar. I

The cathode C preferably has thereon means for progressively turning it on its longitudinal axis, as for example a series of radial arms 33, which are conveniently attached to one of'the extensions 23. The hangers 15, 16 permit of thc cathode pipe turning therein.

In very long articles, the hydro en gas re-.

pipe under ordinary conditions would be so great as to'prevent the deposition of chromium at and toward the ends of the pipe, and even where means were provided for carrying off the hydrogen it would still be difficult in many cases to prevent the excess hydrogen interfering with the plating. Moreover, in such cases, the use of a large amount of current will have a heating effect which would make it difiicult to maintain the roper limits of temperature for chromium p ating. Under these conditions the quantity of current flowing from the anode is reduced by passing only'enough current at a proper current density for depositing the chromium along a longitudinal strip on the inside of the pipe. This is conveniently effected by 10- eating the anode relatively close to the strip on which the deposition is to be. effected and remote from the other portions of the surface, as illustrated most clearly in Fig. 2. As here shown, current at a proper'density for plating passes from the anode to the cathode along a narrow strip, having a width for example of the are between the lines Current may be. saved by shielding the anode from the cathode at those parts of the cathode surface where the current density is below that between the lines klt-. This shielding may be effected by glass or porce- 15, '16 similar to those shown in Figs. 1 to 3,

lain plate or lates 100 having hydrogen -with the plating at the end or ends of the article. As shown in Fi 1, the hydrogen gas rises to the upper inside and part of the cathode, and flows toward and out from the upper end, the flow being assisted by the circulation of the plating solution through the pipe, which circulation may be natural, as shown,'or forced.

The solution (and hydrogen) acts to protect the unplated portions while the plating is going on at the other portions of the inside of the pipe or article. When the pipe along one longitudinal strip has received the proper deposit of chromium, it is turned so that deposition may be efiected along another longitudinal portion. The turning may be either intermittent or continuous, and the turning is continued until the entire surface to be plated has received a chromium deposit.

Referring to Fig. 4, the article C is shown as a long pipe, which is immersed in the electrolytic solution, and which, as here shown, may be suspended in a horizontal position. The sleeves or extensions 22, 23 may be placed on the ends of the cathode pipe, radial arms 33 for turning the cathode pipe, and hangers inclusive, may be provided.

An anode 26 is run through the pipe, and has suitable connections at its end to the anode bus 26'. The'anode may be supported by suitable means inside the pipe. These means may be conveniently a series of glass plates or frames 40 making contact with the inside of the pipe, placed at intervals along the inside of the pipe, and having strips 41 or other" suitable means connecting the anode thereto. These inside supports facilitate the placing of the anode inside of the pipe without coming into contact with the inner prepared walls, it being preferable to avoid such contact in the case of anodes such as are usually used, viz. lead or lead-covered anodes. An imperfect plate usually results where such anodes touch the inside walls.

Means, as a perforated .pipe 45, is intro duced into the cathode pipe, preferably at its upper side, being conveniently supported by the insulating brackets 40. This pipe 45 is provided withopenings or perforations therein, and the excess hydrogen, or the solution containing the greater portion of such excess hydrogen, is drawn ofi'through the pipe 45. Alternatively, portions of the above solution can be introduced into the interior of the cathode pipe through the pipes 45,

- and thereby produce a forced .circulation through the pipe, and thus reducing the con-.

centration of hydrogen in" the bath solution inside the lpipe. I

Prefera ly the hydrogen is drawn off (or the fresh solution introduced) from each end of the pipe, so that the amount of hydrogen,

or solution containing hydrogen, passing out through each end is one-half of what-it would be if it all passed out through one end. This materially increases the amount of current which may be used for depositing the chromium over similar conditions where all of the introduction of liquid or withdrawal of hydrogen is through one end.

In case of long relatively narrow articles, the current, at a sufficient density for depositing chromium, is preferably passed from the anode to a longitudinal strip or portion only of the cathode pipe, and the cathode pipe turned successive y to provide for electrodeposition of chromium over the entire surface, in practically the same manner as heretofore described with reference to Fig. 1.

Referring to Fig. 7, the cathode article C is again shown as a long pipe, and his immersed in the plating solution, preferably in such manner asto leave a space between the upper level of the solution in-the pipe, and the upper surface. The cathode pipe may be suspended from the cathode bus 20 by hangers 15, 16 as described in referenceto Fig. 1, and sleeves or extensions 22, 23 may be placed on its ends, and radialarms 33 be provided for turning the same, also as heretofore described with reference to Fig. 1. The anode 26 is passed through the cathode pipe, and may besupported by glass-plates 40 and strips 41 similar to those illustrated in Fig. 5.

In the case of long articles of relatively small diameter. the current at a proper density for electrodcpositing chromium is passed .from the anode 26 to the cathode C along a strip or longitudinal portion of the inner surface, as for example between the lines k-k,

Fig. 8. The excess hydrogen finds a short path to the space 60, at the upper inside of the pipe, and can flow along said space 60 unopposed by having to, pass through the body of the plating solution, and thereby enables a relatively large quantity of excess hydrogen to be evolved without interfering with the perfect plating of the inside of the pipe. To retard the flow of the hydrogen from the space 60, and to maintain an atmosphere of hydrogen in said space 60, suitable means are placed .at the end or ends of the pipe. These means bubbles of hydrogen. pipe is turned onits longitudinal-axis (as by means of radial arms 33., Fig. 9) one or more times to complete the plating of the inside surface.

Referring to Figs. 10, 11 and 12, the cathode article C is shown as a flanged tube, closed at one end.

The cathode article, Fig. 10, is suspended in a bathb hangers 15, 16similar1y to the cathode article in Fig. 1, the article being inclined and having its open end uppermost, whereby excess hydrogen is removed by gravi- 'tation, assisted b the flow of electrolyte induced by the out ow of the hydrogen. If desired, a perforated pipe 45 may be introduced into the cathode article, through which hydro- .tudinal strip.

, As shown in Fig. 10, the anode 26 is held in a fixed or stationar support 70, and the cathode article turne in relation thereto. One end of the anode, as indicated at 72, near the closed end, is turned up or inward to insure plating to the center of the closed end.

. As shown in Fig. 12, the anode 26 may be arranged in the form of a loop 74, attached to a suitable head 75, carried by shaft 77, and i f be: required for immersing the sheet to, a

depth corresponding to its turned in any suitable manner, as by means 0 a handle 79. In this mode of carrying out the process the anode is rotated progressively either continuously .or step by step whereby to plate longitudinal strips on the inside of the cathode. With the loop or double arrangement, two strips are simultaneously plated.

perforatedpipe may be employed for A witln rawing the excess hydrogen, soas to avoid an excessive concentration at the upper end of the tube. 1

Sleeves or extensions 23 are preferably placed at the open ends of the cathode articles. This permits of the solutionlevel being 7 carried above the upper edge of the tube in bothFigs. 10and12, and assures platingv at the'open ends of the tube, a's heretofore explained. Radial arms 33, may be placed on the extension 23,Fig. 10, as means for turning the cathode article. I'

Referring to Fig. 13, the cathode article 0 is shown as a hollow or tubular article having reduced ends.

Thecathode article C. is'conveniently supported in the bath by passing a shaft 80 through its two'ends, WlllCl'l shaft 80 may be mounted in journals, and turned, by means of a handle 81, for example, to rotate the article,

and it maalso serve as ameans of carrying the oath e current to the cathode article.

The anode,26 is conveniently rod shaped to conform enerallywith the lon 'tudinal contour of t e cathode article, an extends lengthwise thereof, and may. be suspended from the anode bus 26' by means of conductin strips 85, 86, or the like.

e solution level is preferably on aline which passes through the open ends of the cathode article. p

The excess hydrogen as disengaged in the process of the platin' ows upwar through the solution, as descri ed in reference to Fig.-,

7, and flows laterally toward the open ends without having to pass through'the liquid.

Suitable means, such as disks 88, may be placed at the o n ends of the cathode'article so as to partia y close the same, and "thereby restrict the escape of as from the interior of the cathode article, t ereby maintaining a protective atmosphere'of hydro n gas on those portions of the interiorsur ce not bein plated at the time, plating taking place, asieretofore explained, alon a longitudinal strip, andthe cathode article ing turned to obtain progressively a plating extending entirely around the inside surface of the article.

In Figs. 14 and 15 there is illustrated a mode of applyin the process to articles of other than cylin rical form. The. article 0 as, shown is a trough-like article having straight sides and a curved body. The ends mageor may not be closed. Lar e sheets may be nt in the form of a U, and thereby plated in a bath which is moreshallow than would The plating is efl'ected in strips parallel to:

the anode, which, for uniformity of'expression, will bedescribed as longitudinal strips. The U (or J) shaped anode is slid continuously or step by step from'end to end of the 'cathode article, thereby laying down a continuous to Y chromium plate on the-article. The surface not being plated at the time being immersed,

and being cathode, is protected against oxidation, or other influence which would inhibit a good adherent plate of chromipm being later appliedpthereto.

' In Fig. 16there is shown a ineans of shielding the parts of the "cathode 'C'not being plated Q at the time, which means is also a 1 3;

means for concentrating current on parts of the cathode to be plated. As here shown,

the means may be an insulating plate 100 placed around the anode except at the portions opposite the strip or area to be plated. This insulating plate may conveniently be of porcelain or glass, and is provided with openings 101 of any suitable nature at its upper side to enable hydrogen to readily cscape.

The apparatus for electrolytic cleaning may be similar to that used for deposition. The removal of the hydrogen gas from the solution is advantageous, as it reduces the resistance of the solution. However, with acid (used as the bath) which does not have an oxidizing effect on the parts not undergoing the concentrated treatment at the time, the confining means 62, Fig. 7 and 88, Fig. 13 may conveniently be omitted, as the copious hydrogen evolution will usually serve to V prevent atmospheric oxidation.

The invention may be carried out in other modes of procedure than those herein specifically illustrated and described.

What is claimed is 1. In a method of electrodepositing a metal such as chromium accompanied by the disengagement of large quantities of hydrogen, on the inside of hollow articles, removing hydrogen from the solution at localities intermediate the ends whereby the concencles and then current passed from the anode extending longitudinally of said article and making the platin current efiective on a longitudinal strip 0% relatively narrow width therein.

In witness whereof, I have hereunto signed my name.

WARREN AYRES TYRRELL.

tration of hydrogen in the plating solution gagement of large quantitiesof hydrogen, on

the inside or" hollow articles, forcing a circulation of the solution in opposite directions on the interior of said article.

4:. In a method of electrodepositing a metal such as chromium accompanied by the disengagement of large quantities of hydrogen, on

the inside of hollow articles, passing into an anode extending longitudinally of said article less'currentthan the amount required to furnish current at the required current density for plating to the entire inside surface,

and concentrating the current, at the re uired current density vfor plating, along a ongitudinal strip.

5. The process set forth in claim 1 in which extensions are placed on the end or ends of said articles; and then passing current from the anode extending longitudinally of said article.

6. The process set forth in claim 1 in which extensions are placed on the ends of the arti- 

